1. Field of the Invention
This technology relates to a level shifting circuit that changes the maximum and/or minimum voltages between the input and output, such as for a power switch or word line driver.
2. Description of Related Art
A level shifting circuit has multiple stages, with each stage having an output voltage with maximum and/or minimum voltages changed from the input voltage. The maximum output voltage of a particular stage is determined by the supply voltage providing power to that particular stage. Accordingly, different stages of a level shifting circuit receive power from different supply voltages.
However, the use of multiple supply voltages is associated with current leakage. Current leakage occurs from a supply voltage providing a higher voltage to a supply voltage providing a lower voltage.
The multiple supply voltages can be provided by multiple voltage pumps powered by the external voltage, using capacitors to create lower or higher voltage power sources. Multiple voltage pumps have different setup and recovery times, with leakage between the voltage pumps, such as when switching the supply voltage on or off. A voltage pump consumes power to change the voltage of charge, and to lose the voltage pumped charge to leakage represents a waste of power. Current leakage between the multiple supply voltages not only wastes power, it requires more demanding charge pump design to compensate for the current leakage.
One approach to preventing or decreasing the current leakage between different supply voltages, is timing control and level control of the different supply voltages and the signals received by the level shifting circuit. Such timing control and level control minimizes leakage paths through the level shifting circuit, at the cost of the extra circuitry performing the timing control and level control and associated extra power requirements.